Just two days before he was to depart for a state visit to Greece, President Clinton yesterday delayed and shortened his trip in response to a wave of anti-American protests that officials said threatened both his diplomatic goals and his safety.

The sudden change of an overseas itinerary due to political protests is unprecedented during Clinton's seven years in office and is embarrassing to both countries. Although Greece is a NATO ally, many of its citizens are supportive of fellow Orthodox Christians in Serbia and are angry over the U.S.-led bombing campaign against Yugoslavia earlier this year.

Clinton's visit to Greece will now come at the end of his nine-day tour through five European countries, and he will stay in Athens just 22 hours, rather than the two full days that originally had been planned.

The new schedule was announced jointly by the White House and the Greek government, and was presented in both Washington and Athens as a change made at the request of the Greek government. But this request followed two weeks of talks that Clinton administration officials said began when they expressed concern about deteriorating security.

The ill will that is building in Greece is highly unusual for Clinton and his recent predecessors. The president typically receives warm or even ecstatic receptions overseas. There have been occasional protests and embarrassments, such as the hurling of horse manure at his limousine in South America two years ago. But Clinton has never before had to refashion a foreign trip at the last minute because of security concerns.

The situation in Greece is more reminiscent of the street turmoil and anti-Yankee fervor common in parts of Europe during the Cold War. For several days running, half a dozen or more anti-American demonstrations have taken place on the streets of Athens. On Sunday, gunmen on motorcycles fired at the unoccupied American Cultural Center, and a bomb blew up a closed Levi's jeans outlet. A terrorist group calling itself Anti-State Action also has set off bombs at German and French car showrooms, and, just yesterday, at a dealership selling Japanese Suzukis.

Greek Prime Minister Costas Simitis rebuffed a request from U.S. Ambassador Nicholas Burns to deny a permit for several thousand demonstrators to march from Constitution Square in central Athens to the U.S. Embassy on Saturday. That was the day Clinton originally was scheduled to visit the city.

U.S. and Greek officials said yesterday that the terrorism and protests apparently are being orchestrated by Greece's political left, which is more robust than in most European nations. They added, however, that opinion surveys make clear that unease about the Yugoslav war spreads across the political spectrum. Greece formally, though tepidly, supported the 78-day air campaign launched by NATO to stop Serbian ethnic cleansing in Kosovo, but popular opinion among Greeks was overwhelmingly sympathetic to Serbia.

Administration officials say Simitis has put relations with the United States on a better plane than his predecessors did. But he is facing elections in March, which U.S. officials believe has made him reluctant to be seen as stretching to accommodate the White House delegation.

Although Clinton's arrival in Greece will be delayed by less than a week, to Nov. 19 instead of Nov. 13, this could be a significant difference. The new itinerary has him in Athens after Nov. 17, which is a significant date in modern Greek political history, the anniversary of a crackdown against a leftist student uprising in 1973 by a U.S.-backed military junta.

Greece's most notorious terrorist group calls itself November 17 and is believed by authorities to be responsible for killing 22 people, including four U.S. officials. The failure of Greek authorities to arrest anyone for these murders has been a source of considerable tension between the United States and Greece.

White House officials said that during the visit to Greece, Clinton hopes to announce progress on trade issues and to promote an easing of antagonism between Greece and Turkey, particularly over the divided island of Cyprus. They said these goals will be much harder to accomplish if the trip is defined by massive protests. But canceling the visit to Greece altogether would have been diplomatically awkward, since Clinton also plans to stop in Turkey and the United States does not want to convey any favoritism.

Clinton yesterday said he is not worried about his physical safety in Greece.

"Oh, I'm not concerned at all," he said. "You know, if the Greek government and the Secret Service aren't concerned, I'm not concerned." As for protests, he told reporters: "I'm not bothered about it. You know, it's going to happen, and you all get to take pictures of it."

Theodossis Demetracopoulos, a spokesman for the Greek Embassy here, said the protests would not hinder a productive summit. "We're a democracy," he said. "Anyone should be able to peacefully express free speech."

Correspondent R. Jeffrey Smith contributed to this report from Pristina, Yugoslavia.